1. Field of the Invention
The present invention relates to an LCD pixel structure and a method for manufacturing the structure. In particular, the invention relates to an LTPS-LCD pixel structure and a method for manufacturing the structure.
2. Descriptions of the Related Art
Liquid crystal displays (LCDs) are mainstream products on the display market. Not only do LCDs save power and emit low radiation, they are also lightweight and portable. Technologies of thin-film-transistor LCD (TFT-LCD) can be classified into two groups: amorphous silicon (α-Si) and poly-silicon (Poly-Si).
However, low temperature poly silicon (LTPS) is a recent and novel technology for manufacturing Poly-Si LCDs. In comparison with conventional α-Si LCDs, the displays which utilize LTPS technology have higher performance, with shorter response time and greater brightness, resolution, and color saturation. Therefore, LTPS-LCDs can present images with higher display quality. Moreover, the TFT module in the LTPS-LCDs can be minimized and thus the LTPS-LCDs can be thinner and lighter in order to reduce power exhausting. The smaller size advantage of the TFT modules and the LTPS-LCDs also reduces manufacturing costs as well. Because of the many advantages presented by LTPS technology, LTPS-LCDs attract a large portion of the LCD market.
In the conventional LTPS photolithography manufacturing processes, six masks are usually involved. These processes for manufacturing an LPTS-LCD pixel structure 10 are outlined in FIGS. 1A to 1F. For illustration, a TFT 11 and a capacitance storage device 13 are merely shown in the figures. Firstly, FIG. 1A shows the photolithography process with the first mask. Poly-silicon islands 110, 130 are formed onto a substrate 100 to function as fundamental materials for the TFT 11 and the capacitance storage device 13.
Referring to FIG. 1B, the photolithography process with the second mask is illustrated. A lower dielectric layer 12 is formed to cover the aforesaid poly-silicon islands 110, 130. Then, the first conductive layers 113, 133 are respectively formed on the lower dielectric layer 12. Subsequently, as shown the arrows in FIG. 1B, the poly-silicon islands 110 are doped with P+ and P− ions to turn the islands into a source/drain structure.
After, as shown in FIG. 1C, an upper insulator layer 14 covers the aforesaid structures. Two contact holes 141 are then formed by the photolithography process with the third mask. The contact holes 141 are then utilized to expose the source/drain structure for electrical conduction.
The photolithography process with the fourth mask is shown in FIG. 1D. The second conductive layers 115, 135 are formed, in which the second conductive layer 115 connects the source/drain structure within the contact hole 141. The other second conductive layer 135 is correspondingly formed above the first conductive layer 133. As a result, a MIM (metal-insulator-metal) capacitance is formed between the first conductive layer 133 and the second conductive layer 135.
Referring to FIG. 1E, a passivation layer 16 is formed to cover the above mentioned elements. Then, the photolithography process with the fifth mask can be proceeded to form a contact hole 161 for partially exposing the second conductive layer 115 which connects with the drain structure.
Finally, as shown in FIG. 1F, a transparent conductive layer 17 is formed by the photolithography process with the sixth mask. The transparent conductive layer 17 electrically connects with the second conductive layer 115 at the contact hole 161 and further connects to a display area (not shown) of the pixel for providing the required electric fields.
As previously mentioned, at least six masks are involved in the manufacturing of the conventional LTPS-LCD pixel structure 10. Because of the high cost associated with each photolithography process, a manufacturing method with a large number of photolithography processes will result in a higher overall manufacturing cost.
Given the above, an LTPS-LCD pixel structure and a method for manufacturing the structure using less photolithography processes with similar or even more preferable functions need to be developed in this field.